# Perpetual generation of two-photon quantum beats

## TL;DR

This paper proposes a recursive optical device using a Mach-Zehnder interferometer that can generate continuous coherent superpositions of two-photon quantum states through self-feedback mechanisms.

## Contribution

It introduces a novel recursive optical setup capable of perpetually generating two-photon quantum beats using linear optical elements and self-feedback.

## Key findings

- Demonstrates perpetual generation of quantum beats in a recursive optical device.
- Shows that specific input states and arrangements enable continuous superpositions.
- Provides a theoretical framework for sustained quantum state superpositions in linear optics.

## Abstract

We consider a recursive device that is based on a Mach-Zehnder interferometer and linear optical elements which allow self-feedback through multiple internal reflection of radiation between two parallel arrays of opposite faced mirrors. By a carefully chosen experimental arrangement and for certain input states it is possible to observe at the open ends of the device time generated coherent superpositions \textit{in perpetuum}.